Still not true. I'm always suspicious when I see x's on one side of an equation that don't seem to have any way of canceling, and then I don't see them on the RHS of the equation. I do get the following:

Nup, this should definitely be true... unless my University maths professor made the mistake lol

Urm, its actually the end bit of another problem. Maybe you could do the full problem?:

Equation of a circle centre (1, -2) and radius 5 is given by
x^2-y^2-2x+4y-20=0

Show that (d^2.y)/(d.x^2 )=17/(2+y)^3

At the original post, the LHS is d^2y/dx^2, and a = dy/dx.

Aug 4th 2011, 06:33 PM

Umair

Re: Algebraic Simplification

Quote:

Originally Posted by Ackbeet

Still not true. I'm always suspicious when I see x's on one side of an equation that don't seem to have any way of canceling, and then I don't see them on the RHS of the equation. I do get the following:

is not a circle. It is an hyperbola, since the signs of the $\displaystyle x^{2}$ and $\displaystyle y^{2}$ terms are opposite.

Aug 4th 2011, 06:51 PM

Umair

Re: Algebraic Simplification

Ohh quite a few things make sense now! Thank you very much! One question though, is your value of y' supposed to be that? I've re-done my calculation for dy/dx many times and checked that you didn't get my answer for a?

Aug 4th 2011, 07:14 PM

Ackbeet

Re: Algebraic Simplification

I did my calculations in Post # 12 based on the (incorrect) hyperbola equation, not the (correct) circle equation exhibited by skeeter in post # 10. For the correct circle equation, I get the following:

I did my calculations in Post # 12 based on the (incorrect) hyperbola equation, not the (correct) circle equation exhibited by skeeter in post # 10. For the correct circle equation, I get the following: